Solve the equation. The letters a, b, and c are constants and a≠0 ax-7b = 9c

i got confused bc it doesn’t tell me what to solve for. please help! thank you!

Monica build a remote control toy airplane for science project to test the plane she launched it from the top of a building the plane travel a horizontal distance of 50 feet before landing on the ground a quadratic function which models the height of the plane in feet relative to the ground at a horizontal distance of x feet from the building is shown